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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
Randy Dunlapca1eda22009-05-06 16:02:58 -070020Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
Stefan Richtera901ebb2006-04-01 01:43:18 +020026This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
Stefan Richter6585fa82006-04-01 01:44:30 +020033The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100039 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020043 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080045 BLACKFIN Blackfin architecture is enabled.
Randy Dunlapa9913042005-10-23 12:57:11 -070046 DRM Direct Rendering Management support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070051 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050054 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070056 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080057 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020061 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070062 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070071 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070072 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
john stultz734efb42006-06-26 00:25:05 -070075 GENERIC_TIME The generic timeofday code is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070078 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070082 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
James Morris20510f22007-10-16 23:31:32 -070093 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090096 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -070099 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -0500101 FTRACE Function tracing enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500103 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700111 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700114 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116
117In addition, the following text indicates that the option:
118
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
122
123Parameters denoted with BOOT are actually interpreted by the boot
124loader, and have no meaning to the kernel directly.
125Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500126need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127
Karsten Weiss55588702007-02-13 13:26:21 +0100128There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700129See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100130
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132a trailing = on the name of any parameter states that that parameter will
133be entered as an environment variable, whereas its absence indicates that
134it will appear as a kernel argument readable via /proc/cmdline by programs
135running once the system is up.
136
jens m. noedler9c4751f2006-09-29 02:00:27 -0700137The number of kernel parameters is not limited, but the length of the
138complete command line (parameters including spaces etc.) is limited to
139a fixed number of characters. This limit depends on the architecture
140and is between 256 and 4096 characters. It is defined in the file
141./include/asm/setup.h as COMMAND_LINE_SIZE.
142
143
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530144 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800145 Advanced Configuration and Power Interface
Randy Dunlapaf23f572009-02-22 17:05:22 -0800146 Format: { force | off | ht | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
Randy Dunlapa9913042005-10-23 12:57:11 -0700151 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800153 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800154 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155
Randy Dunlap53471122008-03-12 18:10:51 -0400156 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157
Len Browna1fdcc02007-03-11 03:26:14 -0400158 acpi_apic_instance= [ACPI, IOAPIC]
159 Format: <int>
160 2: use 2nd APIC table, if available
161 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400162 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400163
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200164 acpi_backlight= [HW,ACPI]
165 acpi_backlight=vendor
166 acpi_backlight=video
167 If set to vendor, prefer vendor specific driver
168 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
169 of the ACPI video.ko driver.
170
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700171 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
172 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700174 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
175 debug output. Bits in debug_layer correspond to a
176 _COMPONENT in an ACPI source file, e.g.,
177 #define _COMPONENT ACPI_PCI_COMPONENT
178 Bits in debug_level correspond to a level in
179 ACPI_DEBUG_PRINT statements, e.g.,
180 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600181 The debug_level mask defaults to "info". See
182 Documentation/acpi/debug.txt for more information about
183 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600185 Enable processor driver info messages:
186 acpi.debug_layer=0x20000000
187 Enable PCI/PCI interrupt routing info messages:
188 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700189 Enable AML "Debug" output, i.e., stores to the Debug
190 object while interpreting AML:
191 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700192 Enable all messages related to ACPI hardware:
193 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200194
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700195 Some values produce so much output that the system is
196 unusable. The "log_buf_len" parameter may be useful
197 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800198
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700199 acpi_display_output= [HW,ACPI]
200 acpi_display_output=vendor
201 acpi_display_output=video
202 See above.
203
204 acpi_irq_balance [HW,ACPI]
205 ACPI will balance active IRQs
206 default in APIC mode
207
208 acpi_irq_nobalance [HW,ACPI]
209 ACPI will not move active IRQs (default)
210 default in PIC mode
211
212 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
213 Format: <irq>,<irq>...
214
215 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
216 use by PCI
217 Format: <irq>,<irq>...
218
219 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220
221 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
222 Format: To spoof as Windows 98: ="Microsoft Windows"
223
224 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
225 acpi_osi="string1" # add string1 -- only one string
226 acpi_osi="!string2" # remove built-in string2
227 acpi_osi= # disable all strings
228
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530229 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700230 Override the pmtimer bug detection: force the kernel
231 to assume that this machine's pmtimer latches its value
232 and always returns good values.
233
Randy Dunlap4af94f32009-04-17 18:30:28 -0700234 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
235 Format: { level | edge | high | low }
236
237 acpi_serialize [HW,ACPI] force serialization of AML methods
238
239 acpi_skip_timer_override [HW,ACPI]
240 Recognize and ignore IRQ0/pin2 Interrupt Override.
241 For broken nForce2 BIOS resulting in XT-PIC timer.
242
243 acpi_sleep= [HW,ACPI] Sleep options
244 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800245 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700246 See Documentation/power/video.txt for information on
247 s3_bios and s3_mode.
248 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel's real-mode entry point is called.
250 s4_nohwsig prevents ACPI hardware signature from being
251 used during resume from hibernation.
252 old_ordering causes the ACPI 1.0 ordering of the _PTS
253 control method, with respect to putting devices into
254 low power states, to be enforced (the ACPI 2.0 ordering
255 of _PTS is used by default).
256 s4_nonvs prevents the kernel from saving/restoring the
257 ACPI NVS memory during hibernation.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800258 sci_force_enable causes the kernel to set SCI_EN directly
259 on resume from S1/S3 (which is against the ACPI spec,
260 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700261
262 acpi_use_timer_override [HW,ACPI]
263 Use timer override. For some broken Nvidia NF5 boards
264 that require a timer override, but don't have HPET
265
Luca Tettamanti7e905602009-03-30 00:01:27 +0200266 acpi_enforce_resources= [ACPI]
267 { strict | lax | no }
268 Check for resource conflicts between native drivers
269 and ACPI OperationRegions (SystemIO and SystemMemory
270 only). IO ports and memory declared in ACPI might be
271 used by the ACPI subsystem in arbitrary AML code and
272 can interfere with legacy drivers.
273 strict (default): access to resources claimed by ACPI
274 is denied; legacy drivers trying to access reserved
275 resources will fail to bind to device using them.
276 lax: access to resources claimed by ACPI is allowed;
277 legacy drivers trying to access reserved resources
278 will bind successfully but a warning message is logged.
279 no: ACPI OperationRegions are not marked as reserved,
280 no further checks are performed.
281
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 ad1848= [HW,OSS]
283 Format: <io>,<irq>,<dma>,<dma2>,<type>
284
Randy Dunlap4af94f32009-04-17 18:30:28 -0700285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
287
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 advansys= [HW,SCSI]
289 See header of drivers/scsi/advansys.c.
290
291 advwdt= [HW,WDT] Advantech WDT
292 Format: <iostart>,<iostop>
293
294 aedsp16= [HW,OSS] Audio Excel DSP 16
295 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
296 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700297
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700298 agp= [AGP]
299 { off | try_unsupported }
300 off: disable AGP support
301 try_unsupported: try to drive unsupported chipsets
302 (may crash computer or cause data corruption)
303
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304 aha152x= [HW,SCSI]
305 See Documentation/scsi/aha152x.txt.
306
307 aha1542= [HW,SCSI]
308 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309
310 aic7xxx= [HW,SCSI]
311 See Documentation/scsi/aic7xxx.txt.
312
313 aic79xx= [HW,SCSI]
314 See Documentation/scsi/aic79xx.txt.
315
Russell Kingd944d542010-02-20 16:13:29 +0000316 alignment= [KNL,ARM]
317 Allow the default userspace alignment fault handler
318 behaviour to be specified. Bit 0 enables warnings,
319 bit 1 enables fixups, and bit 2 sends a segfault.
320
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200321 amd_iommu= [HW,X86-84]
322 Pass parameters to the AMD IOMMU driver in the system.
323 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900324 fullflush - enable flushing of IO/TLB entries when
325 they are unmapped. Otherwise they are
326 flushed before they will be reused, which
327 is a lot of faster
328
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 amijoy.map= [HW,JOY] Amiga joystick support
330 Map of devices attached to JOY0DAT and JOY1DAT
331 Format: <a>,<b>
332 See also Documentation/kernel/input/joystick.txt
333
334 analog.map= [HW,JOY] Analog joystick and gamepad support
335 Specifies type or capabilities of an analog joystick
336 connected to one of 16 gameports
337 Format: <type1>,<type2>,..<type16>
338
Randy Dunlapa9913042005-10-23 12:57:11 -0700339 apc= [HW,SPARC]
340 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 Format: noidle
342 Disable APC CPU standby support. SPARCstation-Fox does
343 not play well with APC CPU idle - disable it if you have
344 APC and your system crashes randomly.
345
Randy Dunlapca1eda22009-05-06 16:02:58 -0700346 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700347 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348 Format: { quiet (default) | verbose | debug }
349 Change the amount of debugging information output
350 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700351
Brian Haleyb0f83b22010-02-04 13:36:50 -0800352 autoconf= [IPV6]
353 See Documentation/networking/ipv6.txt.
354
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
363
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700365 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
369
370 ataflop= [HW,M68k]
371
372 atarimouse= [HW,MOUSE] Atari Mouse
373
374 atascsi= [HW,SCSI] Atari SCSI
375
376 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
377 EzKey and similar keyboards
378
379 atkbd.reset= [HW] Reset keyboard during initialization
380
Randy Dunlapa9913042005-10-23 12:57:11 -0700381 atkbd.set= [HW] Select keyboard code set
382 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383
384 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 keyboards
386
387 atkbd.softraw= [HW] Choose between synthetic and real raw mode
388 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700389
390 atkbd.softrepeat= [HW]
391 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700392
393 autotest [IA64]
394
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 baycom_epp= [HW,AX25]
396 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700397
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
399 Format: <io>,<mode>
400 See header of drivers/net/hamradio/baycom_par.c.
401
Randy Dunlapa9913042005-10-23 12:57:11 -0700402 baycom_ser_fdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 Format: <io>,<irq>,<mode>[,<baud>]
405 See header of drivers/net/hamradio/baycom_ser_fdx.c.
406
Randy Dunlapa9913042005-10-23 12:57:11 -0700407 baycom_ser_hdx= [HW,AX25]
408 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 Format: <io>,<irq>,<mode>
410 See header of drivers/net/hamradio/baycom_ser_hdx.c.
411
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700412 boot_delay= Milliseconds to delay each printk during boot.
413 Values larger than 10 seconds (10000) are changed to
414 no delay (0).
415 Format: integer
416
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700417 bootmem_debug [KNL] Enable bootmem allocator debug messages.
418
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700420 bttv.radio= Most important insmod options are available as
421 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
423 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
424
425 BusLogic= [HW,SCSI]
426 See drivers/scsi/BusLogic.c, comment before function
427 BusLogic_ParseDriverOptions().
428
429 c101= [NET] Moxa C101 synchronous serial card
430
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700431 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 Sometimes CPU hardware bugs make them report the cache
433 size incorrectly. The kernel will attempt work arounds
434 to fix known problems, but for some CPUs it is not
435 possible to determine what the correct size should be.
436 This option provides an override for these situations.
437
James Morris20510f22007-10-16 23:31:32 -0700438 capability.disable=
439 [SECURITY] Disable capabilities. This would normally
440 be used only if an alternative security model is to be
441 configured. Potentially dangerous and should only be
442 used if you are entirely sure of the consequences.
443
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100444 ccw_timeout_log [S390]
445 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446
Paul Menage8bab8dd2008-04-04 14:29:57 -0700447 cgroup_disable= [KNL] Disable a particular controller
448 Format: {name of the controller(s) to disable}
449 {Currently supported controllers - "memory"}
450
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 checkreqprot [SELINUX] Set initial checkreqprot flag value.
452 Format: { "0" | "1" }
453 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700454 0 -- check protection applied by kernel (includes
455 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 1 -- check protection requested by application.
457 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700458 Value can be changed at runtime via
459 /selinux/checkreqprot.
460
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100461 cio_ignore= [S390]
462 See Documentation/s390/CommonIO for details.
463
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700464 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700465 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200466 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700467 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200468 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469 Format: { pit | tsc | cyclone | pmtmr }
470
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700471 clocksource= [GENERIC_TIME] Override the default clocksource
472 Format: <string>
473 Override the default clocksource and use the clocksource
474 with the name specified.
475 Some clocksource names to choose from, depending on
476 the platform:
477 [all] jiffies (this is the base, fallback clocksource)
478 [ACPI] acpi_pm
479 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
480 pxa_timer,timer3,32k_counter,timer0_1
481 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700482 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700483 scx200_hrt on Geode; cyclone on IBM x440
484 [MIPS] MIPS
485 [PARISC] cr16
486 [S390] tod
487 [SH] SuperH
488 [SPARC64] tick
489 [X86-64] hpet,tsc
490
Andi Kleenac72e782008-01-30 13:33:21 +0100491 clearcpuid=BITNUM [X86]
492 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800493 arch/x86/include/asm/cpufeature.h for the valid bit
494 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100495 stable over kernel options, but the vendor specific
496 ones should be.
497 Also note that user programs calling CPUID directly
498 or using the feature without checking anything
499 will still see it. This just prevents it from
500 being used by the kernel or shown in /proc/cpuinfo.
501 Also note the kernel might malfunction if you disable
502 some critical bits.
503
Robert Jennings14f966e2009-04-15 05:55:32 +0000504 cmo_free_hint= [PPC] Format: { yes | no }
505 Specify whether pages are marked as being inactive
506 when they are freed. This is used in CMO environments
507 to determine OS memory pressure for page stealing by
508 a hypervisor.
509 Default: yes
510
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530511 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100512 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100513 Range: 0 - 8192
514 Default: 64
515
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700517 Format:
518 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519
520 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
521 Format: <io>[,<irq>]
522
Randy Dunlapa9913042005-10-23 12:57:11 -0700523 com90xx= [HW,NET]
524 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 Format: <io>[,<irq>[,<memstart>]]
526
527 condev= [HW,S390] console device
528 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700529
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 console= [KNL] Output console device and options.
531
532 tty<n> Use the virtual console device <n>.
533
534 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800535 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800537 the form "bbbbpnf", where "bbbb" is the baud rate,
538 "p" is parity ("n", "o", or "e"), "n" is number of
539 bits, and "f" is flow control ("r" for RTS or
540 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800542 See Documentation/serial-console.txt for more
543 information. See
544 Documentation/networking/netconsole.txt for an
545 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700546
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700547 uart[8250],io,<addr>[,options]
548 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549 Start an early, polled-mode console on the 8250/16550
550 UART at the specified I/O port or MMIO address,
551 switching to the matching ttyS device later. The
552 options are the same as for ttyS, above.
553
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700554 If the device connected to the port is not a TTY but a braille
555 device, prepend "brl," before the device type, for instance
556 console=brl,ttyS0
557 For now, only VisioBraille is supported.
558
Daniel Mackf324edc2009-06-16 15:33:52 -0700559 consoleblank= [KNL] The console blank (screen saver) timeout in
560 seconds. Defaults to 10*60 = 10mins. A value of 0
561 disables the blank timer.
562
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800563 coredump_filter=
564 [KNL] Change the default value for
565 /proc/<pid>/coredump_filter.
566 See also Documentation/filesystems/proc.txt.
567
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700569 Format:
570 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700572 crashkernel=nn[KMG]@ss[KMG]
573 [KNL] Reserve a chunk of physical memory to
574 hold a kernel to switch to with kexec on panic.
575
Bernhard Wallefb391592007-10-18 23:41:02 -0700576 crashkernel=range1:size1[,range2:size2,...][@offset]
577 [KNL] Same as above, but depends on the memory
578 in the running system. The syntax of range is
579 start-[end] where start and end are both
580 a memory unit (amount[KMG]). See also
581 Documentation/kdump/kdump.txt for a example.
582
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583 cs89x0_dma= [HW,NET]
584 Format: <dma>
585
586 cs89x0_media= [HW,NET]
587 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700588
Randy Dunlapa9913042005-10-23 12:57:11 -0700589 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 See header of drivers/s390/block/dasd_devmap.c.
591
592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
593 (one device per port)
594 Format: <port#>,<type>
595 See also Documentation/input/joystick-parport.txt
596
597 debug [KNL] Enable kernel debugging (events log level).
598
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700599 debug_locks_verbose=
600 [KNL] verbose self-tests
601 Format=<0|1>
602 Print debugging info while doing the locking API
603 self-tests.
604 We default to 0 (no extra messages), setting it to
605 1 will print _a lot_ more information - normally
606 only useful to kernel developers.
607
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700608 debug_objects [KNL] Enable object debugging
609
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500610 no_debug_objects
611 [KNL] Disable object debugging
612
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200613 debugpat [X86] Enable PAT debugging
614
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200615 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 Format: <area>[,<node>]
617 See also Documentation/networking/decnet.txt.
618
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700619 default_hugepagesz=
620 [same as hugepagesz=] The size of the default
621 HugeTLB page size. This is the size represented by
622 the legacy /proc/ hugepages APIs, used for SHM, and
623 default size when mounting hugetlbfs filesystems.
624 Defaults to the default architecture's huge page size
625 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700626
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 dhash_entries= [KNL]
628 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700629
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 digi= [HW,SERIAL]
631 IO parameters + enable/disable command.
632
633 digiepca= [HW,SERIAL]
634 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000635 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636
Brian Haleyb0f83b22010-02-04 13:36:50 -0800637 disable= [IPV6]
638 See Documentation/networking/ipv6.txt.
639
640 disable_ipv6= [IPV6]
641 See Documentation/networking/ipv6.txt.
642
Yinghai Lu95ffa242008-04-29 03:52:33 -0700643 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700644 The kernel tries to adjust MTRR layout from continuous
645 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700646 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700647
Yinghai Lu093af8d2008-01-30 13:33:32 +0100648 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100649 By default the kernel will trim any uncacheable
650 memory out of your available memory pool based on
651 MTRR settings. This parameter disables that behavior,
652 possibly causing your machine to run very slowly.
653
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530654 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700655 Disable PIN 1 of APIC timer
656 Can be useful to work around chipset bugs.
657
Linus Torvalds1da177e2005-04-16 15:20:36 -0700658 dmasound= [HW,OSS] Sound subsystem buffers
659
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700660 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
661 this option disables the debugging code at boot.
662
663 dma_debug_entries=<number>
664 This option allows to tune the number of preallocated
665 entries for DMA-API debugging code. One entry is
666 required per DMA-API allocation. Use this if the
667 DMA-API debugging code disables itself because the
668 architectural default is too low.
669
Joerg Roedel1745de52009-05-22 21:49:51 +0200670 dma_debug_driver=<driver_name>
671 With this option the DMA-API debugging driver
672 filter feature can be enabled at boot time. Just
673 pass the driver to filter for as the parameter.
674 The filter can be disabled or changed to another
675 driver later using sysfs.
676
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677 dscc4.setup= [NET]
678
679 dtc3181e= [HW,SCSI]
680
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700681 dynamic_printk Enables pr_debug()/dev_dbg() calls if
682 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
683 These can also be switched on/off via
684 <debugfs>/dynamic_printk/modules
685
686 earlycon= [KNL] Output early console device and options.
687 uart[8250],io,<addr>[,options]
688 uart[8250],mmio,<addr>[,options]
689 Start an early, polled-mode console on the 8250/16550
690 UART at the specified I/O port or MMIO address.
691 The options are the same as for ttyS, above.
692
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530693 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694 earlyprintk=vga
695 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500696 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500697 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698
Randy Dunlapa9913042005-10-23 12:57:11 -0700699 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 takes over.
701
Yinghai Lu5c059172008-07-24 17:29:40 -0700702 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703
704 Currently only ttyS0 and ttyS1 are supported.
705
706 Interaction with the standard serial driver is not
707 very good.
708
709 The VGA output is eventually overwritten by the real
710 console.
711
712 eata= [HW,SCSI]
713
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700715 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717 eisa_irq_edge= [PARISC,HW]
718 See header of drivers/parisc/eisa.c.
719
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700720 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700722 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700723
724 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800725 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700726 See Documentation/block/as-iosched.txt and
727 Documentation/block/deadline-iosched.txt for details.
728
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530729 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700730 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800731 image elf header. Generally kexec loader will
732 pass this option to capture kernel.
733 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700735 enable_mtrr_cleanup [X86]
736 The kernel tries to adjust MTRR layout from continuous
737 to discrete, to make X server driver able to add WB
738 entry later. This parameter enables that.
739
Randy Dunlapca1eda22009-05-06 16:02:58 -0700740 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700741 Enable PIN 1 of APIC timer
742 Can be useful to work around chipset bugs
743 (in particular on some ATI chipsets).
744 The kernel tries to set a reasonable default.
745
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746 enforcing [SELINUX] Set initial enforcing status.
747 Format: {"0" | "1"}
748 See security/selinux/Kconfig help text.
749 0 -- permissive (log only, no denials).
750 1 -- enforcing (deny and log).
751 Default value is 0.
752 Value can be changed at runtime via /selinux/enforce.
753
Linus Torvalds1da177e2005-04-16 15:20:36 -0700754 ether= [HW,NET] Ethernet cards parameters
755 This option is obsoleted by the "netdev=" option, which
756 has equivalent usage. See its documentation for details.
757
758 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
759 Format: <io>[,<irq>]
760
Akinobu Mitade1ba092006-12-08 02:39:42 -0800761 failslab=
762 fail_page_alloc=
763 fail_make_request=[KNL]
764 General fault injection mechanism.
765 Format: <interval>,<probability>,<space>,<times>
766 See also /Documentation/fault-injection/.
767
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 fd_mcs= [HW,SCSI]
769 See header of drivers/scsi/fd_mcs.c.
770
771 fdomain= [HW,SCSI]
772 See header of drivers/scsi/fdomain.c.
773
774 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000775 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776
Alex Chiangf13ae302008-05-08 14:03:23 -0600777 force_pal_cache_flush
778 [IA-64] Avoid check_sal_cache_flush which may hang on
779 buggy SAL_CACHE_FLUSH implementations. Using this
780 parameter will force ia64_sal_cache_flush to call
781 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
782
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100783 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400784 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100785 as early as possible in order to facilitate early
786 boot debugging.
787
788 ftrace_dump_on_oops
Steven Rostedt2af15d62009-05-28 13:37:24 -0400789 [FTRACE] will dump the trace buffers on oops.
790
791 ftrace_filter=[function-list]
792 [FTRACE] Limit the functions traced by the function
793 tracer at boot up. function-list is a comma separated
794 list of functions. This list can be changed at run
795 time by the set_ftrace_filter file in the debugfs
796 tracing directory.
797
798 ftrace_notrace=[function-list]
799 [FTRACE] Do not trace the functions specified in
800 function-list. This list can be changed at run time
801 by the set_ftrace_notrace file in the debugfs
802 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100803
Stefan Assmann369bc182009-10-12 22:17:21 +0200804 ftrace_graph_filter=[function-list]
805 [FTRACE] Limit the top level callers functions traced
806 by the function graph tracer at boot up.
807 function-list is a comma separated list of functions
808 that can be changed at run time by the
809 set_graph_function file in the debugfs tracing directory.
810
Linus Torvalds1da177e2005-04-16 15:20:36 -0700811 gamecon.map[2|3]=
812 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
813 support via parallel port (up to 5 devices per port)
814 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
815 See also Documentation/input/joystick-parport.txt
816
817 gamma= [HW,DRM]
818
Yinghai Luaaf23042008-01-30 13:33:09 +0100819 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
820 Format: off | on
821 default: on
822
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700823 gcov_persist= [GCOV] When non-zero (default), profiling data for
824 kernel modules is saved and remains accessible via
825 debugfs, even when the module is unloaded/reloaded.
826 When zero, profiling data is discarded and associated
827 debugfs files are removed at module unload time.
828
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829 gdth= [HW,SCSI]
830 See header of drivers/scsi/gdth.c.
831
832 gpt [EFI] Forces disk with valid GPT signature but
833 invalid Protective MBR to be treated as GPT.
834
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835 gvp11= [HW,SCSI]
836
837 hashdist= [KNL,NUMA] Large hashes allocated during boot
838 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700839 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700840 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841
842 hcl= [IA-64] SGI's Hardware Graph compatibility layer
843
844 hd= [EIDE] (E)IDE hard drive subsystem geometry
845 Format: <cyl>,<head>,<sect>
846
Linus Torvalds1da177e2005-04-16 15:20:36 -0700847 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
848 size of <nn>. This works even on boxes that have no
849 highmem otherwise. This also works to reduce highmem
850 size on bigger boxes.
851
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800852 highres= [KNL] Enable/disable high resolution timer mode.
853 Valid parameters: "on", "off"
854 Default: "on"
855
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856 hisax= [HW,ISDN]
857 See Documentation/isdn/README.HiSax.
858
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700859 hlt [BUGS=ARM,SH]
860
861 hpet= [X86-32,HPET] option to control HPET usage
862 Format: { enable (default) | disable | force |
863 verbose }
864 disable: disable HPET and use PIT instead
865 force: allow force enabled of undocumented chips (ICH4,
866 VIA, nVidia)
867 verbose: show contents of HPET registers during setup
868
Andi Kleenb4718e62008-07-23 21:27:51 -0700869 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
870 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700871 On x86-64 and powerpc, this option can be specified
872 multiple times interleaved with hugepages= to reserve
873 huge pages of different sizes. Valid pages sizes on
874 x86-64 are 2M (when the CPU supports "pse") and 1G
875 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700876 Note that 1GB pages can only be allocated at boot time
877 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900878
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100879 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
880 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100881 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
882 If specified, z/VM IUCV HVC accepts connections
883 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100884
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700885 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700886 or register an additional I2C bus that is not
887 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700888 Format:
889 <bus_id>,<clkrate>
890
Jiri Kosina36d95732008-10-06 02:51:09 -0400891 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700892 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200893 i8042.dumbkbd [HW] Pretend that controller can only read data from
894 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895 (Don't attempt to blink the leds)
896 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500897 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400898 i8042.noloop [HW] Disable the AUX Loopback command while probing
899 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700900 i8042.nomux [HW] Don't check presence of an active multiplexing
901 controller
902 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
903 controllers
904 i8042.panicblink=
905 [HW] Frequency with which keyboard LEDs should blink
906 when kernel panics (default is 0.5 sec)
907 i8042.reset [HW] Reset the controller during init and cleanup
908 i8042.unlock [HW] Unlock (ignore) the keylock
909
910 i810= [HW,DRM]
911
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700912 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
913 indicates that the driver is running on unsupported
914 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700915 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
916 does not match list of supported models.
917 i8k.power_status
918 [HW] Report power status in /proc/i8k
919 (disabled by default)
920 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
921 capability is set.
922
923 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
924 See Documentation/mca.txt.
925
926 icn= [HW,ISDN]
927 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
928
David Fries0af80c02009-02-25 20:28:21 +0100929 ide-core.nodma= [HW] (E)IDE subsystem
930 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200931 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
932 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100933 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700935 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
936 Claim all unknown PCI IDE storage controllers.
937
Andi Kleenf039b752007-05-02 19:27:12 +0200938 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800939 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
940 Poll forces a polling idle loop that can slightly
941 improve the performance of waking up a idle CPU, but
942 will use a lot of power and make the system run hot.
943 Not recommended.
944 idle=mwait: On systems which support MONITOR/MWAIT but
945 the kernel chose to not use it because it doesn't save
946 as much power as a normal idle loop, use the
947 MONITOR/MWAIT idle loop anyways. Performance should be
948 the same as idle=poll.
949 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800950 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800951 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700952
Ingo Molnar792908222006-12-06 20:40:51 -0800953 ignore_loglevel [KNL]
954 Ignore loglevel setting - this will print /all/
955 kernel messages to the console. Useful for debugging.
956
Linus Torvalds1da177e2005-04-16 15:20:36 -0700957 ihash_entries= [KNL]
958 Set number of hash buckets for inode cache.
959
Mimi Zohar3323eec92009-02-04 09:06:58 -0500960 ima_audit= [IMA]
961 Format: { "0" | "1" }
962 0 -- integrity auditing messages. (Default)
963 1 -- enable informational integrity auditing messages.
964
965 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700966 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500967 default: "sha1"
968
Eric Paris5789ba32009-05-21 15:47:06 -0400969 ima_tcb [IMA]
970 Load a policy which meets the needs of the Trusted
971 Computing Base. This means IMA will measure all
972 programs exec'd, files mmap'd for exec, and all files
973 opened for read by uid=0.
974
Linus Torvalds1da177e2005-04-16 15:20:36 -0700975 in2000= [HW,SCSI]
976 See header of drivers/scsi/in2000.c.
977
978 init= [KNL]
979 Format: <full_path>
980 Run specified binary instead of /sbin/init as init
981 process.
982
983 initcall_debug [KNL] Trace initcalls as they are executed. Useful
984 for working out where the kernel is dying during
985 startup.
986
987 initrd= [BOOT] Specify the location of the initial ramdisk
988
989 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
990 Format: <irq>
991
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700992 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800993 on
994 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700995 off
996 Disable intel iommu driver.
997 igfx_off [Default Off]
998 By default, gfx is mapped as normal device. If a gfx
999 device has a dedicated DMAR unit, the DMAR unit is
1000 bypassed by not enabling DMAR with this option. In
1001 this case, gfx device will use physical address for
1002 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001003 forcedac [x86_64]
1004 With this option iommu will not optimize to look
1005 for io virtual address below 32 bit forcing dual
1006 address cycle on pci bus for cards supporting greater
1007 than 32 bit addressing. The default is to look
1008 for translation below 32 bit and if not available
1009 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001010 strict [Default Off]
1011 With this option on every unmap_single operation will
1012 result in a hardware IOTLB flush operation as opposed
1013 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001014
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001015 inttest= [IA64]
1016
1017 iomem= Disable strict checking of access to MMIO memory
1018 strict regions from userspace.
1019 relaxed
1020
1021 iommu= [x86]
1022 off
1023 force
1024 noforce
1025 biomerge
1026 panic
1027 nopanic
1028 merge
1029 nomerge
1030 forcesac
1031 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001032 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001033
1034 io7= [HW] IO7 for Marvel based alpha systems
1035 See comment before marvel_specify_io7 in
1036 arch/alpha/kernel/core_marvel.c.
1037
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301038 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001039 0x80
1040 Standard port 0x80 based delay
1041 0xed
1042 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001043 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001044 Simple two microseconds delay
1045 none
1046 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001047
Linus Torvalds1da177e2005-04-16 15:20:36 -07001048 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001049 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050
1051 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001052 See comment before ip2_setup() in
1053 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054
1055 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1056 See header of drivers/scsi/ips.c.
1057
Alan Cox200803d2005-06-28 20:45:18 -07001058 irqfixup [HW]
1059 When an interrupt is not handled search all handlers
1060 for it. Intended to get systems with badly broken
1061 firmware running.
1062
1063 irqpoll [HW]
1064 When an interrupt is not handled search all handlers
1065 for it. Also check all handlers each timer
1066 interrupt. Intended to get systems with badly broken
1067 firmware running.
1068
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001070 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071
1072 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001073 Format:
1074 <cpu number>,...,<cpu number>
1075 or
Li Zefanb225d442008-11-06 12:53:39 -08001076 <cpu number>-<cpu number>
1077 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001078 or a mixture
1079 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001080
Linus Torvalds1da177e2005-04-16 15:20:36 -07001081 This option can be used to specify one or more CPUs
1082 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001083 algorithms. You can move a process onto or off an
1084 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001085 <cpu number> begins at 0 and the maximum value is
1086 "number of CPUs in system - 1".
1087
1088 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001089 alternative -- manually setting the CPU mask of all
1090 tasks in the system -- can cause problems and
1091 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092
Randy Dunlapa9913042005-10-23 12:57:11 -07001093 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094
1095 js= [HW,JOY] Analog joystick
1096 See Documentation/input/joystick.txt.
1097
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001098 keepinitrd [HW,ARM]
1099
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301100 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001101 specifies the amount of memory usable by the kernel
1102 for non-movable allocations. The requested amount is
1103 spread evenly throughout all nodes in the system. The
1104 remaining memory in each node is used for Movable
1105 pages. In the event, a node is too small to have both
1106 kernelcore and Movable pages, kernelcore pages will
1107 take priority and other nodes will have a larger number
1108 of kernelcore pages. The Movable zone is used for the
1109 allocation of pages that may be reclaimed or moved
1110 by the page migration subsystem. This means that
1111 HugeTLB pages may not be allocated from this zone.
1112 Note that allocations like PTEs-from-HighMem still
1113 use the HighMem zone if it exists, and the Normal
1114 zone if it does not.
1115
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001116 kgdboc= [HW] kgdb over consoles.
1117 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001118 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001119 Format: <serial_device>[,baud]
1120
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001121 kmac= [MIPS] korina ethernet MAC address.
1122 Configure the RouterBoard 532 series on-chip
1123 Ethernet adapter MAC address.
1124
Catalin Marinas04f70332009-06-11 13:22:39 +01001125 kmemleak= [KNL] Boot-time kmemleak enable/disable
1126 Valid arguments: on, off
1127 Default: on
1128
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301129 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001130 in oops dumps.
1131
Andre Przywarafef07aa2009-07-10 14:20:35 +02001132 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1133 Default is 0 (don't ignore, but inject #GP)
1134
1135 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1136 Default is 1 (enabled)
1137
1138 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1139 Default is 0 (off)
1140
1141 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1142 for all guests.
1143 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1144
1145 kvm-intel.bypass_guest_pf=
1146 [KVM,Intel] Disables bypassing of guest page faults
1147 on Intel chips. Default is 1 (enabled)
1148
1149 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1150 (virtualized MMU) support on capable Intel chips.
1151 Default is 1 (enabled)
1152
1153 kvm-intel.emulate_invalid_guest_state=
1154 [KVM,Intel] Enable emulation of invalid guest states
1155 Default is 0 (disabled)
1156
1157 kvm-intel.flexpriority=
1158 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159 Default is 1 (enabled)
1160
1161 kvm-intel.unrestricted_guest=
1162 [KVM,Intel] Disable unrestricted guest feature
1163 (virtualized real and unpaged mode) on capable
1164 Intel chips. Default is 1 (enabled)
1165
1166 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167 feature (tagged TLBs) on capable Intel chips.
1168 Default is 1 (enabled)
1169
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 l2cr= [PPC]
1171
Robert Brosea78bfbf2008-03-29 07:20:23 +11001172 l3cr= [PPC]
1173
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001174 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001175 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301177 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001178 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001179
FD Camifcb71f62008-01-06 19:08:56 +01001180 libata.dma= [LIBATA] DMA control
1181 libata.dma=0 Disable all PATA and SATA DMA
1182 libata.dma=1 PATA and SATA Disk DMA only
1183 libata.dma=2 ATAPI (CDROM) DMA only
1184 libata.dma=4 Compact Flash DMA only
1185 Combinations also work, so libata.dma=3 enables DMA
1186 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001187
1188 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1189 libata.ignore_hpa=0 keep BIOS limits (default)
1190 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001191
Dave Jones78e70c22007-09-27 11:50:13 -04001192 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1193 when set.
1194 Format: <int>
1195
Tejun Heo33267322008-02-13 09:15:09 +09001196 libata.force= [LIBATA] Force configurations. The format is comma
1197 separated list of "[ID:]VAL" where ID is
1198 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1199 matching port, link or device. Basically, it matches
1200 the ATA ID string printed on console by libata. If
1201 the whole ID part is omitted, the last PORT and DEVICE
1202 values are used. If ID hasn't been specified yet, the
1203 configuration applies to all ports, links and devices.
1204
1205 If only DEVICE is omitted, the parameter applies to
1206 the port and all links and devices behind it. DEVICE
1207 number of 0 either selects the first device or the
1208 first fan-out link behind PMP device. It does not
1209 select the host link. DEVICE number of 15 selects the
1210 host link and device attached to it.
1211
1212 The VAL specifies the configuration to force. As long
1213 as there's no ambiguity shortcut notation is allowed.
1214 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215 The following configurations can be forced.
1216
1217 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218 Any ID with matching PORT is used.
1219
1220 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1221
1222 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223 udma[/][16,25,33,44,66,100,133] notation is also
1224 allowed.
1225
1226 * [no]ncq: Turn on or off NCQ.
1227
Tejun Heo05944bd2008-08-13 20:19:09 +09001228 * nohrst, nosrst, norst: suppress hard, soft
1229 and both resets.
1230
Tejun Heo33267322008-02-13 09:15:09 +09001231 If there are multiple matching configurations changing
1232 the same attribute, the last one is used.
1233
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001234 lmb=debug [KNL] Enable lmb debug messages.
1235
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001237 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001239 lockd.nlm_grace_period=P [NFS] Assign grace period.
1240 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001242 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1243 Format: <integer>
1244
1245 lockd.nlm_timeout=T [NFS] Assign timeout value.
1246 Format: <integer>
1247
1248 lockd.nlm_udpport=M [NFS] Assign UDP port.
1249 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001250
1251 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1252 Format: <irq>
1253
1254 loglevel= All Kernel Messages with a loglevel smaller than the
1255 console loglevel will be printed to the console. It can
1256 also be changed with klogd or other programs. The
1257 loglevels are defined as follows:
1258
1259 0 (KERN_EMERG) system is unusable
1260 1 (KERN_ALERT) action must be taken immediately
1261 2 (KERN_CRIT) critical conditions
1262 3 (KERN_ERR) error conditions
1263 4 (KERN_WARNING) warning conditions
1264 5 (KERN_NOTICE) normal but significant condition
1265 6 (KERN_INFO) informational
1266 7 (KERN_DEBUG) debug-level messages
1267
1268 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001269 Format: { n | nk | nM }
1270 n must be a power of two. The default size
1271 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001272
Randy Dunlapaccaa242007-10-16 01:29:37 -07001273 logo.nologo [FB] Disables display of the built-in Linux logo.
1274 This may be used to provide more screen space for
1275 kernel log messages and is useful when debugging
1276 kernel boot problems.
1277
Linus Torvalds1da177e2005-04-16 15:20:36 -07001278 lp=0 [LP] Specify parallel ports to use, e.g,
1279 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1280 lp=reset first parallel port). 'lp=0' disables the
1281 lp=auto printer driver. 'lp=reset' (which can be
1282 specified in addition to the ports) causes
1283 attached printers to be reset. Using
1284 lp=port1,port2,... specifies the parallel ports
1285 to associate lp devices with, starting with
1286 lp0. A port specification may be 'none' to skip
1287 that lp device, or a parport name such as
1288 'parport0'. Specifying 'lp=auto' instead of a
1289 port specification list means that device IDs
1290 from each port should be examined, to see if
1291 an IEEE 1284-compliant printer is attached; if
1292 so, the driver will manage that printer.
1293 See also header of drivers/char/lp.c.
1294
1295 lpj=n [KNL]
1296 Sets loops_per_jiffy to given constant, thus avoiding
1297 time-consuming boot-time autodetection (up to 250 ms per
1298 CPU). 0 enables autodetection (default). To determine
1299 the correct value for your kernel, boot with normal
1300 autodetection and see what value is printed. Note that
1301 on SMP systems the preset will be applied to all CPUs,
1302 which is likely to cause problems if your CPUs need
1303 significantly divergent settings. An incorrect value
1304 will cause delays in the kernel to be wrong, leading to
1305 unpredictable I/O errors and other breakage. Although
1306 unlikely, in the extreme case this might damage your
1307 hardware.
1308
1309 ltpc= [NET]
1310 Format: <io>,<irq>,<dma>
1311
Randy Dunlapa9913042005-10-23 12:57:11 -07001312 mac5380= [HW,SCSI] Format:
1313 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314
Randy Dunlapa9913042005-10-23 12:57:11 -07001315 machvec= [IA64] Force the use of a particular machine-vector
1316 (machvec) in a generic kernel.
1317 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318
Wu Zhangjin3209e702009-07-02 23:27:12 +08001319 machtype= [Loongson] Share the same kernel image file between different
1320 yeeloong laptop.
1321 Example: machtype=lemote-yeeloong-2f-7inch
1322
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001323 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1324 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325
1326 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001327 should make use of. maxcpus=n : n >= 0 limits the
1328 kernel to using 'n' processors. n=0 is a special case,
1329 it is equivalent to "nosmp", which also disables
1330 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001332 max_loop= [LOOP] Maximum number of loopback devices that can
1333 be mounted
1334 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001335
Randy Dunlapa9913042005-10-23 12:57:11 -07001336 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337 Should be between 1 and 2^32-1.
1338
1339 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001340 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001341 Should be between 1 and 16384.
1342
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 mcatest= [IA-64]
1344
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001345 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346
Uwe Hermann71cced62008-10-20 09:32:21 -07001347 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001348
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 md= [HW] RAID subsystems devices and level
1350 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001351
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352 mdacon= [MDA]
1353 Format: <first>,<last>
1354 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001355
Linus Torvalds1da177e2005-04-16 15:20:36 -07001356 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1357 Amount of memory to be used when the kernel is not able
1358 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001359 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 address space collisions. Without memmap= PCI devices
1361 could be placed at addresses belonging to unused RAM.
1362
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001363 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 memory.
1365
Paul Mundt6902aa82008-09-21 17:14:42 +09001366 memchunk=nn[KMG]
1367 [KNL,SH] Allow user to override the default size for
1368 per-device physically contiguous DMA buffers.
1369
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301370 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 E820 memory map, as specified by the user.
1372 Such memmap=exactmap lines can be constructed based on
1373 BIOS output or other requirements. See the memmap=nn@ss
1374 option description.
1375
1376 memmap=nn[KMG]@ss[KMG]
1377 [KNL] Force usage of a specific region of memory
1378 Region of memory to be used, from ss to ss+nn.
1379
1380 memmap=nn[KMG]#ss[KMG]
1381 [KNL,ACPI] Mark specific memory as ACPI data.
1382 Region of memory to be used, from ss to ss+nn.
1383
1384 memmap=nn[KMG]$ss[KMG]
1385 [KNL,ACPI] Mark specific memory as reserved.
1386 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001387 Example: Exclude memory from 0x18690000-0x1869ffff
1388 memmap=64K$0x18690000
1389 or
1390 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001391
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001392 memory_corruption_check=0/1 [X86]
1393 Some BIOSes seem to corrupt the first 64k of
1394 memory when doing things like suspend/resume.
1395 Setting this option will scan the memory
1396 looking for corruption. Enabling this will
1397 both detect corruption and prevent the kernel
1398 from using the memory being corrupted.
1399 However, its intended as a diagnostic tool; if
1400 repeatable BIOS-originated corruption always
1401 affects the same memory, you can use memmap=
1402 to prevent the kernel from using that memory.
1403
1404 memory_corruption_check_size=size [X86]
1405 By default it checks for corruption in the low
1406 64k, making this memory unavailable for normal
1407 use. Use this parameter to scan for
1408 corruption in more or less memory.
1409
1410 memory_corruption_check_period=seconds [X86]
1411 By default it checks for corruption every 60
1412 seconds. Use this parameter to check at some
1413 other rate. 0 disables periodic checking.
1414
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001415 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001416 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001417 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001418 Specifies the number of memtest passes to be
1419 performed. Each pass selects another test
1420 pattern from a given set of patterns. Memtest
1421 fills the memory with this pattern, validates
1422 memory contents and reserves bad memory
1423 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001424
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425 meye.*= [HW] Set MotionEye Camera parameters
1426 See Documentation/video4linux/meye.txt.
1427
Andres Salomon8f368812007-10-12 23:04:06 +02001428 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1429 Multi-Function General Purpose Timers on AMD Geode
1430 platforms.
1431
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001432 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1433 the BIOS has incorrectly applied a workaround. TinyBIOS
1434 version 0.98 is known to be affected, 0.99 fixes the
1435 problem by letting the user disable the workaround.
1436
Linus Torvalds1da177e2005-04-16 15:20:36 -07001437 mga= [HW,DRM]
1438
Randy Dunlap1c207f92008-11-19 15:36:16 -08001439 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1440 physical address is ignored.
1441
Michel Pollet39f45d72009-05-20 11:10:31 +01001442 mini2440= [ARM,HW,KNL]
1443 Format:[0..2][b][c][t]
1444 Default: "0tb"
1445 MINI2440 configuration specification:
1446 0 - The attached screen is the 3.5" TFT
1447 1 - The attached screen is the 7" TFT
1448 2 - The VGA Shield is attached (1024x768)
1449 Leaving out the screen size parameter will not load
1450 the TFT driver, and the framebuffer will be left
1451 unconfigured.
1452 b - Enable backlight. The TFT backlight pin will be
1453 linked to the kernel VESA blanking code and a GPIO
1454 LED. This parameter is not necessary when using the
1455 VGA shield.
1456 c - Enable the s3c camera interface.
1457 t - Reserved for enabling touchscreen support. The
1458 touchscreen support is not enabled in the mainstream
1459 kernel as of 2.6.30, a preliminary port can be found
1460 in the "bleeding edge" mini2440 support kernel at
1461 http://repo.or.cz/w/linux-2.6/mini2440.git
1462
Mel Gorman6b74ab92008-07-23 21:26:49 -07001463 mminit_loglevel=
1464 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1465 parameter allows control of the logging verbosity for
1466 the additional memory initialisation checks. A value
1467 of 0 disables mminit logging and a level of 4 will
1468 log everything. Information is printed at KERN_DEBUG
1469 so loglevel=8 may also need to be specified.
1470
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471 mousedev.tap_time=
1472 [MOUSE] Maximum time between finger touching and
1473 leaving touchpad surface for touch to be considered
1474 a tap and be reported as a left button click (for
1475 touchpads working in absolute mode only).
1476 Format: <msecs>
1477 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1478 reporting absolute coordinates, such as tablets
1479 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1480 reporting absolute coordinates, such as tablets
1481
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301482 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001483 is similar to kernelcore except it specifies the
1484 amount of memory used for migratable allocations.
1485 If both kernelcore and movablecore is specified,
1486 then kernelcore will be at *least* the specified
1487 value but may be more. If movablecore on its own
1488 is specified, the administrator must be careful
1489 that the amount of memory usable for all allocations
1490 is not too small.
1491
Linus Torvalds1da177e2005-04-16 15:20:36 -07001492 mpu401= [HW,OSS]
1493 Format: <io>,<irq>
1494
1495 MTD_Partition= [MTD]
1496 Format: <name>,<region-number>,<size>,<offset>
1497
Randy Dunlapa9913042005-10-23 12:57:11 -07001498 MTD_Region= [MTD] Format:
1499 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500
1501 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001502 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001504 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1505
1506 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1507
1508 boundary - index of last SLC block on Flex-OneNAND.
1509 The remaining blocks are configured as MLC blocks.
1510 lock - Configure if Flex-OneNAND boundary should be locked.
1511 Once locked, the boundary cannot be changed.
1512 1 indicates lock status, 0 indicates unlock status.
1513
Ben Dooks9db829f2008-07-03 11:24:29 +01001514 mtdset= [ARM]
1515 ARM/S3C2412 JIVE boot control
1516
1517 See arch/arm/mach-s3c2412/mach-jive.c
1518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001520 [HW] Make the MicroTouch USB driver use raw coordinates
1521 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001522
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001523 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001524 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001525 that could hold holes aka. UC entries.
1526
1527 mtrr_gran_size=nn[KMG] [X86]
1528 Used for mtrr cleanup. It is granularity of mtrr block.
1529 Default is 1.
1530 Large value could prevent small alignment from
1531 using up MTRRs.
1532
1533 mtrr_spare_reg_nr=n [X86]
1534 Format: <integer>
1535 Range: 0,7 : spare reg number
1536 Default : 1
1537 Used for mtrr cleanup. It is spare mtrr entries number.
1538 Set to 2 or more if your graphical card needs more.
1539
Linus Torvalds1da177e2005-04-16 15:20:36 -07001540 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1541
1542 NCR_D700= [HW,SCSI]
1543 See header of drivers/scsi/NCR_D700.c.
1544
1545 ncr5380= [HW,SCSI]
1546
1547 ncr53c400= [HW,SCSI]
1548
1549 ncr53c400a= [HW,SCSI]
1550
1551 ncr53c406a= [HW,SCSI]
1552
1553 ncr53c8xx= [HW,SCSI]
1554
1555 netdev= [NET] Network devices parameters
1556 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1557 Note that mem_start is often overloaded to mean
1558 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001559 This usage is only documented in each driver source
1560 file if at all.
1561
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001562 nf_conntrack.acct=
1563 [NETFILTER] Enable connection tracking flow accounting
1564 0 to disable accounting
1565 1 to enable accounting
1566 Default value depends on CONFIG_NF_CT_ACCT that is
1567 going to be removed in 2.6.29.
1568
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001570 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571
1572 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001573 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574
Trond Myklebusta72b4422006-01-03 09:55:41 +01001575 nfs.callback_tcpport=
1576 [NFS] set the TCP port on which the NFSv4 callback
1577 channel should listen.
1578
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001579 nfs.cache_getent=
1580 [NFS] sets the pathname to the program which is used
1581 to update the NFS client cache entries.
1582
1583 nfs.cache_getent_timeout=
1584 [NFS] sets the timeout after which an attempt to
1585 update a cache entry is deemed to have failed.
1586
Trond Myklebust58df0952006-01-03 09:55:57 +01001587 nfs.idmap_cache_timeout=
1588 [NFS] set the maximum lifetime for idmapper cache
1589 entries.
1590
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001591 nfs.enable_ino64=
1592 [NFS] enable 64-bit inode numbers.
1593 If zero, the NFS client will fake up a 32-bit inode
1594 number for the readdir() and stat() syscalls instead
1595 of returning the full 64-bit number.
1596 The default is to return 64-bit inode numbers.
1597
Paul Mundt1e1030d2009-09-01 17:38:32 +09001598 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001599 when a NMI is triggered.
1600 Format: [state][,regs][,debounce][,die]
1601
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301602 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001603 Format: [panic,][num]
1604 Valid num: 0,1,2
1605 0 - turn nmi_watchdog off
1606 1 - use the IO-APIC timer for the NMI watchdog
1607 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001608 a performance counter. Note: This will use one
1609 performance counter and the local APIC's performance
1610 vector.
1611 When panic is specified, panic when an NMI watchdog
1612 timeout occurs.
1613 This is useful when you use a panic=... timeout and
1614 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001615 Instead of 1 and 2 it is possible to use the following
1616 symbolic names: lapic and ioapic
1617 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618
Anton Vorontsovbff38772009-07-08 11:10:56 -07001619 netpoll.carrier_timeout=
1620 [NET] Specifies amount of time (in seconds) that
1621 netpoll should wait for a carrier. By default netpoll
1622 waits 4 seconds.
1623
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001624 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625 emulation library even if a 387 maths coprocessor
1626 is present.
1627
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001628 no_console_suspend
1629 [HW] Never suspend the console
1630 Disable suspending of consoles during suspend and
1631 hibernate operations. Once disabled, debugging
1632 messages can reach various consoles while the rest
1633 of the system is being put to sleep (ie, while
1634 debugging driver suspend/resume hooks). This may
1635 not work reliably with all consoles, but is known
1636 to work with serial and VGA consoles.
1637
Christoph Lameterc1aee212007-05-31 00:40:47 -07001638 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1639 caches in the slab allocator. Saves per-node memory,
1640 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001641
Randy Dunlapa9913042005-10-23 12:57:11 -07001642 noalign [KNL,ARM]
1643
Linus Torvalds1da177e2005-04-16 15:20:36 -07001644 noapic [SMP,APIC] Tells the kernel to not make use of any
1645 IOAPICs that may be present in the system.
1646
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 nobats [PPC] Do not use BATs for mapping kernel lowmem
1648 on "Classic" PPC cores.
1649
1650 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001651
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001652 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1653
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001654 nodelayacct [KNL] Disable per-task delay accounting
1655
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1657
Paul Mundt6902aa82008-09-21 17:14:42 +09001658 nodsp [SH] Disable hardware DSP at boot time.
1659
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301660 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001661
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 noexec [IA-64]
1663
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301664 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001665 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001667 noexec=off: disable non-executable mappings
1668
1669 noexec32 [X86-64]
1670 This affects only 32-bit executables.
1671 noexec32=on: enable non-executable mappings (default)
1672 read doesn't imply executable mappings
1673 noexec32=off: disable non-executable mappings
1674 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001675
Paul Mundt6902aa82008-09-21 17:14:42 +09001676 nofpu [SH] Disable hardware FPU at boot time.
1677
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001678 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001679 register save and restore. The kernel will only save
1680 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681
Suresh Siddha0c752a92009-05-22 12:17:45 -07001682 noxsave [BUGS=X86] Disables x86 extended register state save
1683 and restore using xsave. The kernel will fallback to
1684 enabling legacy floating-point and sse state.
1685
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001686 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1687 wfi(ARM) instruction doesn't work correctly and not to
1688 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001689
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001690 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001691 instruction doesn't work correctly and not to
1692 use it.
1693
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001694 no_file_caps Tells the kernel not to honor file capabilities. The
1695 only way then for a file to be executed with privilege
1696 is to be setuid root or executed by root.
1697
Linus Torvalds1da177e2005-04-16 15:20:36 -07001698 nohalt [IA-64] Tells the kernel not to use the power saving
1699 function PAL_HALT_LIGHT when idle. This increases
1700 power-consumption. On the positive side, it reduces
1701 interrupt wake-up latency, which may improve performance
1702 in certain environments such as networked servers or
1703 real-time systems.
1704
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001705 nohz= [KNL] Boottime enable/disable dynamic ticks
1706 Valid arguments: on, off
1707 Default: on
1708
Paul Mundteeee7852009-04-02 12:31:16 +09001709 noiotrap [SH] Disables trapped I/O port accesses.
1710
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001711 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001712 disable unhandled interrupt sources.
1713
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301714 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001715 broken timer IRQ sources.
1716
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717 noisapnp [ISAPNP] Disables ISA PnP code.
1718
1719 noinitrd [RAM] Tells the kernel not to load any configured
1720 initial RAM disk.
1721
Weidong Han03ea8152009-04-17 16:42:15 +08001722 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1723 remapping.
1724
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725 nointroute [IA-64]
1726
Tony Luck0aa366f2007-07-20 11:22:30 -07001727 nojitter [IA64] Disables jitter checking for ITC timers.
1728
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001729 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001731 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001732
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 noltlbs [PPC] Do not use large page/tlb entries for kernel
1734 lowmem mapping on PPC40x.
1735
Horms312f1f02006-02-22 09:57:55 +09001736 nomca [IA-64] Disable machine check abort handling
1737
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001738 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001739
Andres Salomon83d73842007-10-12 23:04:06 +02001740 nomfgpt [X86-32] Disable Multi-Function General Purpose
1741 Timer usage (for AMD Geode machines).
1742
Jiri Kosina016ddd92010-01-18 17:05:40 +01001743 nopat [X86] Disable PAT (page attribute table extension of
1744 pagetables) support.
1745
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001746 norandmaps Don't use address space randomization. Equivalent to
1747 echo 0 > /proc/sys/kernel/randomize_va_space
1748
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001749 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001750
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001751 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001752 with UP alternatives
1753
Linus Torvalds1da177e2005-04-16 15:20:36 -07001754 noresidual [PPC] Don't use residual data on PReP machines.
1755
Randy Dunlapa9913042005-10-23 12:57:11 -07001756 noresume [SWSUSP] Disables resume and restores original swap
1757 space.
1758
Linus Torvalds1da177e2005-04-16 15:20:36 -07001759 no-scroll [VGA] Disables scrollback.
1760 This is required for the Braillex ib80-piezo Braille
1761 reader made by F.H. Papenmeier (Germany).
1762
1763 nosbagart [IA-64]
1764
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001765 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001766
Len Brown61ec7562007-08-16 03:34:22 -04001767 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1768 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769
Dave Jones97842212007-07-15 23:41:05 -07001770 nosoftlockup [KNL] Disable the soft-lockup detector.
1771
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001772 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001773 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001774
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775 nosync [HW,M68K] Disables sync negotiation for all devices.
1776
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001777 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001778
1779 nousb [USB] Disable the USB subsystem
1780
1781 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001782
Weidong Han2b2fd872009-04-17 16:42:12 +08001783 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1784
Fenghua Yua6c75b862008-03-14 13:57:08 -07001785 nptcg= [IA64] Override max number of concurrent global TLB
1786 purges which is reported from either PAL_VM_SUMMARY or
1787 SAL PALO.
1788
Yinghai Lu2b633e32010-02-10 01:20:37 -08001789 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1790 could support. nr_cpus=n : n >= 1 limits the kernel to
1791 supporting 'n' processors. Later in runtime you can not
1792 use hotplug cpu feature to put more cpu back to online.
1793 just like you compile the kernel NR_CPUS=n
1794
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001795 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1796
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001797 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1798 one of ['zone', 'node', 'default'] can be specified
1799 This can be set from sysctl after boot.
1800 See Documentation/sysctl/vm.txt for details.
1801
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001802 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1803 See Documentation/debugging-via-ohci1394.txt for more
1804 info.
1805
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001806 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1807 Rather than timing out after 20 ms if an EC
1808 command is not properly ACKed, override the length
1809 of the timeout. We have interrupts disabled while
1810 waiting for the ACK, so if this is set too high
1811 interrupts *may* be lost!
1812
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001813 omap_mux= [OMAP] Override bootloader pin multiplexing.
1814 Format: <mux_mode0.mode_name=value>...
1815 For example, to override I2C bus2:
1816 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1817
Linus Torvalds1da177e2005-04-16 15:20:36 -07001818 opl3= [HW,OSS]
1819 Format: <io>
1820
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 oprofile.timer= [HW]
1822 Use timer interrupt instead of performance counters
1823
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001824 oprofile.cpu_type= Force an oprofile cpu type
1825 This might be useful if you have an older oprofile
1826 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001827 Format: { arch_perfmon }
1828 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001829 perfmon on Intel CPUs instead of the
1830 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001831
Linus Torvalds1da177e2005-04-16 15:20:36 -07001832 osst= [HW,SCSI] SCSI Tape Driver
1833 Format: <buffer_size>,<write_threshold>
1834 See also Documentation/scsi/st.txt.
1835
1836 panic= [KNL] Kernel behaviour on panic
1837 Format: <timeout>
1838
1839 parkbd.port= [HW] Parallel port number the keyboard adapter is
1840 connected to, default is 0.
1841 Format: <parport#>
1842 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1843 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001844 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845
Randy Dunlapa9913042005-10-23 12:57:11 -07001846 parport= [HW,PPT] Specify parallel ports. 0 disables.
1847 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1848 Use 'auto' to force the driver to use any
1849 IRQ/DMA settings detected (the default is to
1850 ignore detected IRQ/DMA settings because of
1851 possible conflicts). You can specify the base
1852 address, IRQ, and DMA settings; IRQ and DMA
1853 should be numbers, or 'auto' (for using detected
1854 settings on that particular port), or 'nofifo'
1855 (to avoid using a FIFO even if it is detected).
1856 Parallel ports are assigned in the order they
1857 are specified on the command line, starting
1858 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001859
Randy Dunlapa9913042005-10-23 12:57:11 -07001860 parport_init_mode= [HW,PPT]
1861 Configure VIA parallel port to operate in
1862 a specific mode. This is necessary on Pegasos
1863 computer where firmware has no options for setting
1864 up parallel port mode and sets it to spp.
1865 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866 Format: [spp|ps2|epp|ecp|ecpepp]
1867
Randy Dunlapa9913042005-10-23 12:57:11 -07001868 pas2= [HW,OSS] Format:
1869 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1870
Linus Torvalds1da177e2005-04-16 15:20:36 -07001871 pas16= [HW,SCSI]
1872 See header of drivers/scsi/pas16.c.
1873
Andrew Mortondd287792006-03-23 03:00:57 -08001874 pause_on_oops=
1875 Halt all CPUs after the first oops has been printed for
1876 the specified number of seconds. This is to be used if
1877 your oopses keep scrolling off the screen.
1878
Linus Torvalds1da177e2005-04-16 15:20:36 -07001879 pcbit= [HW,ISDN]
1880
1881 pcd. [PARIDE]
1882 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001883 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884
Randy Dunlapa9913042005-10-23 12:57:11 -07001885 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001886 earlydump [X86] dump PCI config space before the kernel
1887 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001888 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001889 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001890 the hardware directly. Use this if your machine
1891 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001892 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001893 hardware access methods are allowed. Use this
1894 if you experience crashes upon bootup and you
1895 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001896 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001897 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001898 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001899 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001900 noaer [PCIE] If the PCIEAER kernel config parameter is
1901 enabled, this kernel boot option can be used to
1902 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea72007-10-11 16:57:27 -04001903 nodomains [PCI] Disable support for multiple PCI
1904 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301905 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001906 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001907 check_enable_amd_mmconf [X86] check for and enable
1908 properly configured MMIO access to PCI
1909 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001910 nomsi [MSI] If the PCI_MSI kernel config parameter is
1911 enabled, this kernel boot option can be used to
1912 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001913 noioapicquirk [APIC] Disable all boot interrupt quirks.
1914 Safety option to keep boot IRQs enabled. This
1915 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001916 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1917 primary IO-APIC for bridges that cannot disable
1918 boot IRQs. This fixes a source of spurious IRQs
1919 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001920 noioapicreroute [APIC] Disable workaround that uses the
1921 boot IRQ equivalent of an IRQ that connects to
1922 a chipset where boot IRQs cannot be disabled.
1923 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001924 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001925 routing table. These calls are known to be buggy
1926 on several machines and they hang the machine
1927 when used, but on other computers it's the only
1928 way to get the interrupt routing table. Try
1929 this option if the kernel is unable to allocate
1930 IRQs or discover secondary PCI buses on your
1931 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001932 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001933 Use with caution as certain devices share
1934 address decoders between ROMs and other
1935 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001936 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001937 expansion ROMs that do not already have
1938 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001939 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001940 assigned automatically to PCI devices. You can
1941 make the kernel exclude IRQs of your ISA cards
1942 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001943 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001944 of the PIRQ table (normally generated
1945 by the BIOS) if it is outside the
1946 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001947 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001948 useful if the kernel is unable to find your
1949 secondary buses and you want to tell it
1950 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001951 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001952 numbers ourselves, overriding
1953 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001954 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001955 in the BIOS $PIR table. This is needed on
1956 some systems with broken BIOSes, notably
1957 some HP Pavilion N5400 and Omnibook XE3
1958 notebooks. This will have no effect if ACPI
1959 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001960 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001961 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001962 use_crs [X86] Use PCI host bridge window information
1963 from ACPI. On BIOSes from 2008 or later, this
1964 is enabled by default. If you need to use this,
1965 please report a bug.
1966 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1967 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001968 routeirq Do IRQ routing for all PCI devices.
1969 This is normally done in pci_enable_device(),
1970 so this option is a temporary workaround
1971 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001972 skip_isa_align [X86] do not align io start addr, so can
1973 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001974 firmware [ARM] Do not re-enumerate the bus but instead
1975 just use the configuration from the
1976 bootloader. This is currently used on
1977 IXP2000 systems where the bus has to be
1978 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001979 noearly [X86] Don't do any early type 1 scanning.
1980 This might help on some broken boards which
1981 machine check when some devices' config space
1982 is read. But various workarounds are disabled
1983 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001984 bfsort Sort PCI devices into breadth-first order.
1985 This sorting is done to get a device
1986 order compatible with older (<= 2.4) kernels.
1987 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001988 cbiosize=nn[KMG] The fixed amount of bus space which is
1989 reserved for the CardBus bridge's IO window.
1990 The default value is 256 bytes.
1991 cbmemsize=nn[KMG] The fixed amount of bus space which is
1992 reserved for the CardBus bridge's memory
1993 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001994 resource_alignment=
1995 Format:
1996 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1997 Specifies alignment and device to reassign
1998 aligned memory resources.
1999 If <order of align> is not specified,
2000 PAGE_SIZE is used as alignment.
2001 PCI-PCI bridge can be specified, if resource
2002 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002003 ecrc= Enable/disable PCIe ECRC (transaction layer
2004 end-to-end CRC checking).
2005 bios: Use BIOS/firmware settings. This is the
2006 the default.
2007 off: Turn ECRC off
2008 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002009
Chuck Ebberte5665a42008-09-24 20:40:34 -04002010 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2011 Management.
2012 off Disable ASPM.
2013 force Enable ASPM even on devices that claim not to support it.
2014 WARNING: Forcing ASPM on may cause system lockups.
2015
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002016 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2017 off Do not use native PCIe PME signaling.
2018 force Use native PCIe PME signaling even if the BIOS refuses
2019 to allow the kernel to control the relevant PCIe config
2020 registers.
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002021 nomsi Do not use MSI for native PCIe PME signaling (this makes
2022 all PCIe root ports use INTx for everything).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002023
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024 pcmv= [HW,PCMCIA] BadgePAD 4
2025
2026 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002027 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002028
2029 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2030 boot time.
2031 Format: { 0 | 1 }
2032 See arch/parisc/kernel/pdc_chassis.c
2033
Tejun Heof58dc012009-08-14 15:00:50 +09002034 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002035 Currently supported values are "embed" and "page".
2036 Archs may support subset or none of the selections.
2037 See comments in mm/percpu.c for details on each
2038 allocator. This parameter is primarily for debugging
2039 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002040
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002042 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002043
2044 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002045 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046
2047 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002048 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002049
2050 plip= [PPT,NET] Parallel port network link
2051 Format: { parport<nr> | timid | 0 }
2052 See also Documentation/parport.txt.
2053
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002054 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2055 Override pmtimer IOPort with a hex value.
2056 e.g. pmtmr=0x508
2057
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002058 pnp.debug [PNP]
2059 Enable PNP debug messages. This depends on the
2060 CONFIG_PNP_DEBUG_MESSAGES option.
2061
Linus Torvalds1da177e2005-04-16 15:20:36 -07002062 pnpacpi= [ACPI]
2063 { off }
2064
2065 pnpbios= [ISAPNP]
2066 { on | off | curr | res | no-curr | no-res }
2067
2068 pnp_reserve_irq=
2069 [ISAPNP] Exclude IRQs for the autoconfiguration
2070
2071 pnp_reserve_dma=
2072 [ISAPNP] Exclude DMAs for the autoconfiguration
2073
2074 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002075 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002076
2077 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002078 [ISAPNP] Exclude memory regions for the
2079 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002080 Ranges are in pairs (memory base and size).
2081
Randy Dunlap4af94f32009-04-17 18:30:28 -07002082 ports= [IP_VS_FTP] IPVS ftp helper module
2083 Default is 21.
2084 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2085 may be specified.
2086 Format: <port>,<port>....
2087
Ingo Molnar45807a12007-07-15 23:40:10 -07002088 print-fatal-signals=
2089 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002090
2091 If enabled, warn about various signal handling
2092 related application anomalies: too many signals,
2093 too many POSIX.1 timers, fatal signals causing a
2094 coredump - etc.
2095
2096 If you hit the warning due to signal overflow,
2097 you might want to try "ulimit -i unlimited".
2098
Ingo Molnar45807a12007-07-15 23:40:10 -07002099 default: off.
2100
Randy Dunlape84845c2007-07-15 23:40:25 -07002101 printk.time= Show timing data prefixed to each printk message line
2102 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2103
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002104 processor.max_cstate= [HW,ACPI]
2105 Limit processor to maximum C-state
2106 max_cstate=9 overrides any DMI blacklist limit.
2107
2108 processor.nocst [HW,ACPI]
2109 Ignore the _CST method to determine C-states,
2110 instead using the legacy FADT method
2111
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002113 Format: [schedule,]<number>
2114 Param: "schedule" - profile schedule points.
2115 Param: <number> - step/bucket size as a power of 2 for
2116 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002117 Param: "sleep" - profile D-state sleeping (millisecs).
2118 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002119 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002120
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2122 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002123 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002124
Randy Dunlapa9913042005-10-23 12:57:11 -07002125 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2126 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2128 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002129 psmouse.resetafter= [HW,MOUSE]
2130 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002131 (0 = never).
2132 psmouse.resolution=
2133 [HW,MOUSE] Set desired mouse resolution, in dpi.
2134 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002135 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002136 0 = disabled, 1 = enabled (default).
2137
2138 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002139 Format:
2140 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002141
2142 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002143 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002144
Kay Sieversdc8c8582007-08-15 12:25:38 +02002145 pty.legacy_count=
2146 [KNL] Number of legacy pty's. Overwrites compiled-in
2147 default number.
2148
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002149 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002150
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 r128= [HW,DRM]
2152
2153 raid= [HW,RAID]
2154 See Documentation/md.txt.
2155
Randy Dunlapa9913042005-10-23 12:57:11 -07002156 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002157 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002158
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002160 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002162 rcupdate.blimit= [KNL,BOOT]
2163 Set maximum number of finished RCU callbacks to process
2164 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002165
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002166 rcupdate.qhimark= [KNL,BOOT]
2167 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002168 RCU callbacks over which batch limiting is disabled.
2169
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002170 rcupdate.qlowmark= [KNL,BOOT]
2171 Set threshold of queued RCU callbacks below which
2172 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002173
Olof Johanssonffdfc402005-09-06 15:17:19 -07002174 rdinit= [KNL]
2175 Format: <full_path>
2176 Run specified binary instead of /init from the ramdisk,
2177 used for early userspace startup. See initrd.
2178
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002179 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002181 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002182
Paul Jackson46b6d942008-07-04 10:00:09 -07002183 relax_domain_level=
2184 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002185 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002186
Linus Torvalds1da177e2005-04-16 15:20:36 -07002187 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2188
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002189 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07002190 Format: nn[KMG]
2191 Reserves a hole at the top of the kernel virtual
2192 address space.
2193
Vivek Goyal7e962872006-09-27 01:50:44 -07002194 reset_devices [KNL] Force drivers to reset the underlying device
2195 during initialization.
2196
Randy Dunlapa9913042005-10-23 12:57:11 -07002197 resume= [SWSUSP]
2198 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002199
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002200 resume_offset= [SWSUSP]
2201 Specify the offset from the beginning of the partition
2202 given by "resume=" at which the swap header is located,
2203 in <PAGE_SIZE> units (needed only for swap files).
2204 See Documentation/power/swsusp-and-swap-files.txt
2205
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002206 retain_initrd [RAM] Keep initrd memory after extraction
2207
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208 rhash_entries= [KNL,NET]
2209 Set number of hash buckets for route cache
2210
2211 riscom8= [HW,SERIAL]
2212 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2213
2214 ro [KNL] Mount root device read-only on boot
2215
2216 root= [KNL] Root filesystem
2217
2218 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2219 mount the root filesystem
2220
2221 rootflags= [KNL] Set root filesystem mount option string
2222
2223 rootfstype= [KNL] Set root filesystem type
2224
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002225 rootwait [KNL] Wait (indefinitely) for root device to show up.
2226 Useful for devices that are detected asynchronously
2227 (e.g. USB and MMC devices).
2228
Linus Torvalds1da177e2005-04-16 15:20:36 -07002229 rw [KNL] Mount root device read-write on boot
2230
2231 S [KNL] Run init in single mode
2232
2233 sa1100ir [NET]
2234 See drivers/net/irda/sa1100_ir.c.
2235
Linus Torvalds1da177e2005-04-16 15:20:36 -07002236 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002237
Mike Travisf6630112009-11-17 18:22:15 -06002238 sched_debug [KNL] Enables verbose scheduler debug messages.
2239
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2241 Format: <io>[,<timeout>[,<isapnp>]]
2242
2243 scsi_debug_*= [SCSI]
2244 See drivers/scsi/scsi_debug.c.
2245
2246 scsi_default_dev_flags=
2247 [SCSI] SCSI default device flags
2248 Format: <integer>
2249
2250 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2251 Format: <vendor>:<model>:<flags>
2252 (flags are integer value)
2253
Randy Dunlap6af66322007-11-14 16:52:25 -08002254 scsi_logging_level= [SCSI] a bit mask of logging levels
2255 See drivers/scsi/scsi_logging.h for bits. Also
2256 settable via sysctl at dev.scsi.logging_level
2257 (/proc/sys/dev/scsi/logging_level).
2258 There is also a nice 'scsi_logging_level' script in the
2259 S390-tools package, available for download at
2260 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002261
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002262 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2263 discovered. async scans them in kernel threads,
2264 allowing boot to proceed. none ignores them, expecting
2265 user space to do the scan.
2266
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002267 security= [SECURITY] Choose a security module to enable at boot.
2268 If this boot parameter is not specified, only the first
2269 security module asking for security registration will be
2270 loaded. An invalid security module name will be treated
2271 as if no module has been chosen.
2272
2273 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274 Format: { "0" | "1" }
2275 See security/selinux/Kconfig help text.
2276 0 -- disable.
2277 1 -- enable.
2278 Default value is set via kernel config option.
2279 If enabled at boot time, /selinux/disable can be used
2280 later to disable prior to initial policy load.
2281
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002282 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002283
Linus Torvalds1da177e2005-04-16 15:20:36 -07002284 shapers= [NET]
2285 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002286
Yinghai Lub05f78f2008-08-22 01:32:50 -07002287 show_msr= [x86] show boot-time MSR settings
2288 Format: { <integer> }
2289 Show boot-time (BIOS-initialized) MSR settings.
2290 The parameter means the number of CPUs to show,
2291 for example 1 means boot CPU only.
2292
Linus Torvalds1da177e2005-04-16 15:20:36 -07002293 sim710= [SCSI,HW]
2294 See header of drivers/scsi/sim710.c.
2295
2296 simeth= [IA-64]
2297 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002298
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299 slram= [HW,MTD]
2300
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002301 slub_debug[=options[,slabs]] [MM, SLUB]
2302 Enabling slub_debug allows one to determine the
2303 culprit if slab objects become corrupted. Enabling
2304 slub_debug can create guard zones around objects and
2305 may poison objects when not in use. Also tracks the
2306 last alloc / free. For more information see
2307 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002308
2309 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002310 Determines the maximum allowed order for slabs.
2311 A high setting may cause OOMs due to memory
2312 fragmentation. For more information see
2313 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002314
2315 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002316 The minimum number of objects per slab. SLUB will
2317 increase the slab order up to slub_max_order to
2318 generate a sufficiently large slab able to contain
2319 the number of objects indicated. The higher the number
2320 of objects the smaller the overhead of tracking slabs
2321 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002322 For more information see Documentation/vm/slub.txt.
2323
2324 slub_min_order= [MM, SLUB]
2325 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002326 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002327 For more information see Documentation/vm/slub.txt.
2328
2329 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002330 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002331 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002332 allocs to different slabs. Debug options disable
2333 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002334 For more information see Documentation/vm/slub.txt.
2335
Linus Torvalds1da177e2005-04-16 15:20:36 -07002336 smart2= [HW]
2337 Format: <io1>[,<io2>[,...,<io8>]]
2338
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002339 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002340 attempt to substitute SMP alternatives once at boot.
2341
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002342 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2343 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2344 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2345 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2346 smsc-ircc2.ircc_irq= [HW] IRQ line
2347 smsc-ircc2.ircc_dma= [HW] DMA channel
2348 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2349 0: Toshiba Satellite 1800 (GP data pin select)
2350 1: Fast pin select (default)
2351 2: ATC IRMode
2352
Linus Torvalds1da177e2005-04-16 15:20:36 -07002353 snd-ad1816a= [HW,ALSA]
2354
2355 snd-ad1848= [HW,ALSA]
2356
2357 snd-ali5451= [HW,ALSA]
2358
2359 snd-als100= [HW,ALSA]
2360
2361 snd-als4000= [HW,ALSA]
2362
2363 snd-azt2320= [HW,ALSA]
2364
2365 snd-cmi8330= [HW,ALSA]
2366
2367 snd-cmipci= [HW,ALSA]
2368
2369 snd-cs4231= [HW,ALSA]
2370
2371 snd-cs4232= [HW,ALSA]
2372
2373 snd-cs4236= [HW,ALSA]
2374
2375 snd-cs4281= [HW,ALSA]
2376
2377 snd-cs46xx= [HW,ALSA]
2378
2379 snd-dt019x= [HW,ALSA]
2380
2381 snd-dummy= [HW,ALSA]
2382
2383 snd-emu10k1= [HW,ALSA]
2384
2385 snd-ens1370= [HW,ALSA]
2386
2387 snd-ens1371= [HW,ALSA]
2388
2389 snd-es968= [HW,ALSA]
2390
2391 snd-es1688= [HW,ALSA]
2392
2393 snd-es18xx= [HW,ALSA]
2394
2395 snd-es1938= [HW,ALSA]
2396
2397 snd-es1968= [HW,ALSA]
2398
2399 snd-fm801= [HW,ALSA]
2400
2401 snd-gusclassic= [HW,ALSA]
2402
2403 snd-gusextreme= [HW,ALSA]
2404
2405 snd-gusmax= [HW,ALSA]
2406
2407 snd-hdsp= [HW,ALSA]
2408
2409 snd-ice1712= [HW,ALSA]
2410
2411 snd-intel8x0= [HW,ALSA]
2412
2413 snd-interwave= [HW,ALSA]
2414
2415 snd-interwave-stb=
2416 [HW,ALSA]
2417
2418 snd-korg1212= [HW,ALSA]
2419
2420 snd-maestro3= [HW,ALSA]
2421
2422 snd-mpu401= [HW,ALSA]
2423
2424 snd-mtpav= [HW,ALSA]
2425
2426 snd-nm256= [HW,ALSA]
2427
2428 snd-opl3sa2= [HW,ALSA]
2429
2430 snd-opti92x-ad1848=
2431 [HW,ALSA]
2432
2433 snd-opti92x-cs4231=
2434 [HW,ALSA]
2435
2436 snd-opti93x= [HW,ALSA]
2437
2438 snd-pmac= [HW,ALSA]
2439
2440 snd-rme32= [HW,ALSA]
2441
2442 snd-rme96= [HW,ALSA]
2443
2444 snd-rme9652= [HW,ALSA]
2445
2446 snd-sb8= [HW,ALSA]
2447
2448 snd-sb16= [HW,ALSA]
2449
2450 snd-sbawe= [HW,ALSA]
2451
2452 snd-serial= [HW,ALSA]
2453
2454 snd-sgalaxy= [HW,ALSA]
2455
2456 snd-sonicvibes= [HW,ALSA]
2457
2458 snd-sun-amd7930=
2459 [HW,ALSA]
2460
2461 snd-sun-cs4231= [HW,ALSA]
2462
2463 snd-trident= [HW,ALSA]
2464
2465 snd-usb-audio= [HW,ALSA,USB]
2466
2467 snd-via82xx= [HW,ALSA]
2468
2469 snd-virmidi= [HW,ALSA]
2470
2471 snd-wavefront= [HW,ALSA]
2472
2473 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002474
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002475 softlockup_panic=
2476 [KNL] Should the soft-lockup detector generate panics.
2477
Linus Torvalds1da177e2005-04-16 15:20:36 -07002478 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2479 See Documentation/sonypi.txt
2480
2481 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002482 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002483
2484 spia_io_base= [HW,MTD]
2485 spia_fio_base=
2486 spia_pedr=
2487 spia_peddr=
2488
2489 sscape= [HW,OSS]
2490 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002491
Linus Torvalds1da177e2005-04-16 15:20:36 -07002492 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2493 See Documentation/scsi/st.txt.
2494
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002495 stacktrace [FTRACE]
2496 Enabled the stack tracer on boot up.
2497
Linus Torvalds1da177e2005-04-16 15:20:36 -07002498 sti= [PARISC,HW]
2499 Format: <num>
2500 Set the STI (builtin display/keyboard on the HP-PARISC
2501 machines) console (graphic card) which should be used
2502 as the initial boot-console.
2503 See also comment in drivers/video/console/sticore.c.
2504
2505 sti_font= [HW]
2506 See comment in drivers/video/console/sticore.c.
2507
2508 stifb= [HW]
2509 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2510
Trond Myklebustcbf11072009-08-09 15:06:19 -04002511 sunrpc.min_resvport=
2512 sunrpc.max_resvport=
2513 [NFS,SUNRPC]
2514 SunRPC servers often require that client requests
2515 originate from a privileged port (i.e. a port in the
2516 range 0 < portnr < 1024).
2517 An administrator who wishes to reserve some of these
2518 ports for other uses may adjust the range that the
2519 kernel's sunrpc client considers to be privileged
2520 using these two parameters to set the minimum and
2521 maximum port values.
2522
Greg Banks42a7fc42007-03-06 01:42:23 -08002523 sunrpc.pool_mode=
2524 [NFS]
2525 Control how the NFS server code allocates CPUs to
2526 service thread pools. Depending on how many NICs
2527 you have and where their interrupts are bound, this
2528 option will affect which CPUs will do NFS serving.
2529 Note: this parameter cannot be changed while the
2530 NFS server is running.
2531
2532 auto the server chooses an appropriate mode
2533 automatically using heuristics
2534 global a single global pool contains all CPUs
2535 percpu one pool for each CPU
2536 pernode one pool for each NUMA node (equivalent
2537 to global on non-NUMA machines)
2538
Trond Myklebustcbf11072009-08-09 15:06:19 -04002539 sunrpc.tcp_slot_table_entries=
2540 sunrpc.udp_slot_table_entries=
2541 [NFS,SUNRPC]
2542 Sets the upper limit on the number of simultaneous
2543 RPC calls that can be sent from the client to a
2544 server. Increasing these values may allow you to
2545 improve throughput, but will also increase the
2546 amount of memory reserved for use by the client.
2547
Linus Torvalds1da177e2005-04-16 15:20:36 -07002548 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002549
Linus Torvalds1da177e2005-04-16 15:20:36 -07002550 switches= [HW,M68k]
2551
2552 sym53c416= [HW,SCSI]
2553 See header of drivers/scsi/sym53c416.c.
2554
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002555 sysrq_always_enabled
2556 [KNL]
2557 Ignore sysrq setting - this boot parameter will
2558 neutralize any effect of /proc/sys/kernel/sysrq.
2559 Useful for debugging.
2560
Linus Torvalds1da177e2005-04-16 15:20:36 -07002561 t128= [HW,SCSI]
2562 See header of drivers/scsi/t128.c.
2563
2564 tdfx= [HW,DRM]
2565
David Brownell77437fd2008-07-23 21:28:33 -07002566 test_suspend= [SUSPEND]
2567 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2568 standby suspend) as the system sleep state to briefly
2569 enter during system startup. The system is woken from
2570 this state using a wakeup-capable RTC alarm.
2571
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572 thash_entries= [KNL,NET]
2573 Set number of hash buckets for TCP connection
2574
Len Brownf8707ec2007-08-12 00:12:54 -04002575 thermal.act= [HW,ACPI]
2576 -1: disable all active trip points in all thermal zones
2577 <degrees C>: override all lowest active trip points
2578
Len Brownc52a7412007-08-14 15:49:32 -04002579 thermal.crt= [HW,ACPI]
2580 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002581 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002582
Len Brownf5487142007-08-12 00:12:44 -04002583 thermal.nocrt= [HW,ACPI]
2584 Set to disable actions on ACPI thermal zone
2585 critical and hot trip points.
2586
Len Brown72b33ef2007-08-12 00:12:17 -04002587 thermal.off= [HW,ACPI]
2588 1: disable ACPI thermal control
2589
Len Browna70cdc52007-08-12 00:12:35 -04002590 thermal.psv= [HW,ACPI]
2591 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002592 <degrees C>: override all passive trip points to this
2593 value
Len Browna70cdc52007-08-12 00:12:35 -04002594
Len Brown730ff342007-08-12 00:12:26 -04002595 thermal.tzp= [HW,ACPI]
2596 Specify global default ACPI thermal zone polling rate
2597 <deci-seconds>: poll all this frequency
2598 0: no polling (default)
2599
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 tmscsim= [HW,SCSI]
2601 See comment before function dc390_setup() in
2602 drivers/scsi/tmscsim.c.
2603
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002604 topology= [S390]
2605 Format: {off | on}
2606 Specify if the kernel should make use of the cpu
2607 topology informations if the hardware supports these.
2608 The scheduler will make use of these informations and
2609 e.g. base its process migration decisions on it.
2610 Default is off.
2611
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612 tp720= [HW,PS2]
2613
Li Zefan9d612be2009-06-24 17:33:15 +08002614 trace_buf_size=nn[KMG]
2615 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002616
Li Zefan020e5f82009-07-01 10:47:05 +08002617 trace_event=[event-list]
2618 [FTRACE] Set and start specified trace events in order
2619 to facilitate early boot debugging.
2620 See also Documentation/trace/events.txt
2621
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002623 Format:
2624 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2625
Alok Kataria395628e2008-10-24 17:22:01 -07002626 tsc= Disable clocksource-must-verify flag for TSC.
2627 Format: <string>
2628 [x86] reliable: mark tsc clocksource as reliable, this
2629 disables clocksource verification at runtime.
2630 Used to enable high-resolution timer mode on older
2631 hardware, and in virtualized environment.
2632
Randy Dunlapa9913042005-10-23 12:57:11 -07002633 turbografx.map[2|3]= [HW,JOY]
2634 TurboGraFX parallel port interface
2635 Format:
2636 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002637 See also Documentation/input/joystick-parport.txt
2638
2639 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2640 See header of drivers/scsi/u14-34f.c.
2641
2642 uart401= [HW,OSS]
2643 Format: <io>,<irq>
2644
2645 uart6850= [HW,OSS]
2646 Format: <io>,<irq>
2647
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002648 uhash_entries= [KNL,NET]
2649 Set number of hash buckets for UDP/UDP-Lite connections
2650
Alan Stern5f8364b2006-12-05 16:29:55 -05002651 uhci-hcd.ignore_oc=
2652 [USB] Ignore overcurrent events (default N).
2653 Some badly-designed motherboards generate lots of
2654 bogus events, for ports that aren't wired to
2655 anything. Set this parameter to avoid log spamming.
2656 Note that genuine overcurrent events won't be
2657 reported either.
2658
Simon Arlotte3a61b02008-07-19 23:32:54 +01002659 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302660 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002661 Set unknown_nmi_panic=1 early on boot.
2662
Alan Sternb5e795f2007-02-20 15:00:53 -05002663 usbcore.autosuspend=
2664 [USB] The autosuspend time delay (in seconds) used
2665 for newly-detected USB devices (default 2). This
2666 is the time required before an idle device will be
2667 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002668 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002669
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002670 usbcore.usbfs_snoop=
2671 [USB] Set to log all usbfs traffic (default 0 = off).
2672
2673 usbcore.blinkenlights=
2674 [USB] Set to cycle leds on hubs (default 0 = off).
2675
2676 usbcore.old_scheme_first=
2677 [USB] Start with the old device initialization
2678 scheme (default 0 = off).
2679
2680 usbcore.use_both_schemes=
2681 [USB] Try the other device initialization scheme
2682 if the first one fails (default 1 = enabled).
2683
2684 usbcore.initial_descriptor_timeout=
2685 [USB] Specifies timeout for the initial 64-byte
2686 USB_REQ_GET_DESCRIPTOR request in milliseconds
2687 (default 5000 = 5.0 seconds).
2688
Linus Torvalds1da177e2005-04-16 15:20:36 -07002689 usbhid.mousepoll=
2690 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002691
Alan Sternd4f373e2008-11-10 14:07:45 -05002692 usb-storage.delay_use=
2693 [UMS] The delay in seconds before a new device is
2694 scanned for Logical Units (default 5).
2695
2696 usb-storage.quirks=
2697 [UMS] A list of quirks entries to supplement or
2698 override the built-in unusual_devs list. List
2699 entries are separated by commas. Each entry has
2700 the form VID:PID:Flags where VID and PID are Vendor
2701 and Product ID values (4-digit hex numbers) and
2702 Flags is a set of characters, each corresponding
2703 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002704 a = SANE_SENSE (collect more than 18 bytes
2705 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002706 b = BAD_SENSE (don't collect more than 18
2707 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002708 c = FIX_CAPACITY (decrease the reported
2709 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002710 h = CAPACITY_HEURISTICS (decrease the
2711 reported device capacity by one
2712 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002713 i = IGNORE_DEVICE (don't bind to this
2714 device);
2715 l = NOT_LOCKABLE (don't try to lock and
2716 unlock ejectable media);
2717 m = MAX_SECTORS_64 (don't transfer more
2718 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002719 o = CAPACITY_OK (accept the capacity
2720 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002721 r = IGNORE_RESIDUE (the device reports
2722 bogus residue values);
2723 s = SINGLE_LUN (the device has only one
2724 Logical Unit);
2725 w = NO_WP_DETECT (don't test whether the
2726 medium is write-protected).
2727 Example: quirks=0419:aaf5:rl,0421:0433:rc
2728
Ian Campbell14315592010-02-17 10:38:10 +00002729 userpte=
2730 [X86] Flags controlling user PTE allocations.
2731
2732 nohigh = do not allocate PTE pages in
2733 HIGHMEM regardless of setting
2734 of CONFIG_HIGHPTE.
2735
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302736 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002737 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002738 vdso=1: enable VDSO (default)
2739 vdso=0: disable VDSO mapping
2740
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302741 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002742 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2743 vdso32=1: enable 32-bit VDSO (default)
2744 vdso32=0: disable 32-bit VDSO mapping
2745
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002746 vector= [IA-64,SMP]
2747 vector=percpu: enable percpu vector domain
2748
Linus Torvalds1da177e2005-04-16 15:20:36 -07002749 video= [FB] Frame buffer configuration
2750 See Documentation/fb/modedb.txt.
2751
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002752 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002753 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002754 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002755 Use vga=ask for menu.
2756 This is actually a boot loader parameter; the value is
2757 passed to the kernel using a special protocol.
2758
Randy Dunlapa9913042005-10-23 12:57:11 -07002759 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002760 size of <nn>. This can be used to increase the
2761 minimum size (128MB on x86). It can also be used to
2762 decrease the size and leave more room for directly
2763 mapped kernel RAM.
2764
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002765 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2766 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002768 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2769 Format: <command>
2770
2771 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2772 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002773
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002774 vt.cur_default= [VT] Default cursor shape.
2775 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2776 the parameters of the <Esc>[?A;B;Cc escape sequence;
2777 see VGA-softcursor.txt. Default: 2 = underline.
2778
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002779 vt.default_blu= [VT]
2780 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2781 Change the default blue palette of the console.
2782 This is a 16-member array composed of values
2783 ranging from 0-255.
2784
2785 vt.default_grn= [VT]
2786 Format: <green0>,<green1>,<green2>,...,<green15>
2787 Change the default green palette of the console.
2788 This is a 16-member array composed of values
2789 ranging from 0-255.
2790
2791 vt.default_red= [VT]
2792 Format: <red0>,<red1>,<red2>,...,<red15>
2793 Change the default red palette of the console.
2794 This is a 16-member array composed of values
2795 ranging from 0-255.
2796
2797 vt.default_utf8=
2798 [VT]
2799 Format=<0|1>
2800 Set system-wide default UTF-8 mode for all tty's.
2801 Default is 1, i.e. UTF-8 mode is enabled for all
2802 newly opened terminals.
2803
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002804 vt.global_cursor_default=
2805 [VT]
2806 Format=<-1|0|1>
2807 Set system-wide default for whether a cursor
2808 is shown on new VTs. Default is -1,
2809 i.e. cursors will be created by default unless
2810 overridden by individual drivers. 0 will hide
2811 cursors, 1 will display them.
2812
Linus Torvalds1da177e2005-04-16 15:20:36 -07002813 waveartist= [HW,OSS]
2814 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002815
Linus Torvalds1da177e2005-04-16 15:20:36 -07002816 wd33c93= [HW,SCSI]
2817 See header of drivers/scsi/wd33c93.c.
2818
2819 wd7000= [HW,SCSI]
2820 See header of drivers/scsi/wd7000.c.
2821
2822 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002823 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002825 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2826 default x2apic cluster mode on platforms
2827 supporting x2apic.
2828
Jacob Panbb24c472009-09-02 07:37:17 -07002829 x86_mrst_timer= [X86-32,APBT]
2830 Choose timer option for x86 Moorestown MID platform.
2831 Two valid options are apbt timer only and lapic timer
2832 plus one apbt timer for broadcast timer.
2833 x86_mrst_timer=apbt_only | lapic_and_apbt
2834
Linus Torvalds1da177e2005-04-16 15:20:36 -07002835 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2836 xd_geo= See header of drivers/block/xd.c.
2837
2838 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002839 Format:
2840 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002841
Randy Dunlapa9913042005-10-23 12:57:11 -07002842______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002843
2844TODO:
2845
2846 Add documentation for ALSA options.
2847 Add more DRM drivers.